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M13BACTERIOPHAGE
PRESENTEDBY
D.S.ANANTHALAKSHMI
3��rdyearmicrobiology
syedammalartsandcollege,
ramanathapuram.

SYNOPSIS
? INTRODUCTIONOFM13BACTERIOPHAGE
? CHARACTERISTICS
? STRUCTUREOF M13
? GENOMEOF M13
? INFECTION
? APPLICATIONOF VIRALGENOME
? PHAGEPACKAGING
? SECONDSTRANDSYNTHESIS: SSDNA- RF
? MULTIPLICATIONOF RF
? AMPLIFICATIONOF SSDNA: RF - SSDNA
? APPLICATION
?ADVANTAGESOF M13
? DISADVANTAGEM13
? REFERANCES

? Bacteriophage , also known as phages or bacterial viruses are a
group of viruses that infect bacteria .
? They were discovered independently by FREDRICK .W.TWORT (1915)
and FELIX D HERELLE (1917)
? There are several bacteriophages. Among those,m13
bacteriophages is a virus that infect E.COLI bacterium.

CHARACTERISICS
?M13 is a filamentous bacteriophages .
?It has a circular single stranded DNA .
?It is a INOVIRIDAE family .
?The M13 term is derived from city of MUNICH , first isolated by HOTSCHNEIDER In 1963
.
?The genome codes for a total of 10 genes.
?GENE VII codes for the major structural protein of the bacteriophage particles .
?GENE III for the minor protein forms a tubular array of approximately 2700 identical
submits surrounding the viral genome .
?Approximately 5-8 copies of the gene III protein are located at he ends pf the phages .
?It attaches to the receptor at the receptors at the tip of the bacterial �� SEX �� pilus .

? 900 nm long and 9 nm diameter
? The capsid made up of 1 major protein and 4 minor protein .
? 1 major protein - phage GENE VIII { g8p}
? 4 minor protein - gIII , gVI , gVII , gIX
? They are present in 2700 - 3000 copies of proteins .
? combine to 1 major and 4 minor proteins .
? The minor capsid proteins are located in M13 particles present in
end of filamentous .
? M13 bacteriophages appearances alpha helix and look like a shot
rod .
? It is a 6407 base pairs long .
? The genome codes named using Roman numbers { I - X ]

INFECTION
�� Single strand genome { + strand } attached to pilus enter host cell .
[i]Gene VIII - Stripped off
[ii] Gene III - Remains attached
�� Most components convert single strand {+} genome to ds DNA called replicative /��RF�� form.
��Transcription begins
series of promoters
Provide a gradient of transcription such that gene nearest the two transcription terminators are
transcribed the most .
Two terminators
One at the end of gene VIII
One at the end of gene IV
Transcription of all to genes proceeds in same direction .

AMPLIFICATION OF VIRAL GENOME
? Gene II Protein introduces �� nick �� in [+] Strand .
? Polymerase I extendes the [+] strand using STRAND DISPLACEMENT and the [-] Strand
as template .
? After one trip around the genome , the gene II Protein nicks again to release a
complete [+] genome . { linear }
? Linear [+] genome is circularifed .
? during the first 15 - 20 mina of replication the progeny strands are converted into
double stranded form [ RF]
? These serve as additional templates for further transcription .
?GENE V protein builds up .
? it is a single stranded DNA binding protein .
? It prevent the conversion of single [+] Strand to the RF form .
?Now , get a buildup of circular single stranded [+] DNA { M13 GENOME }

PHAGE PACKAGING
? Major coat protein [ gene VIII ] Present in E.Coli membrance
? M13 [+] genome , covered in SS binding Protein . GENE V Protein , move to
cell membrane .
? Gene V Protein stripped off and the major coat protein [GENE VIII]
?COVERS PHAGE DNA as it is etruded out .
? Packaging process is therfore not linked to any size constraint of the M13
Genome .
? Length of the filamentous phage is determined by size of the DNA in the
genome .
?Inserts upto 42 kb introduced into M13 genome and package [ 7 * genome
size ]
?Approximately 8 copies of the extruded genome .

I) SECOND STRAND SYNTHESIS : SS
DNA - RF

Ananthalakshmi [m13 bacteriophage].pptx

APPLICATIONS
? M13 phage vectors are very useful for a precise DNA SEQUENCING .
[ Using both strands of DNA molecule]
? M13 phage vectors are useful for synthesis of specific RADIO -
LABELLED DNA Probes .
? The ss form M13 phage genome is ideally suited for the sanger
sequencing protocal and for many protocols for site directely
Mutagenesis .

ADVANTAGE OF M13 PHAGE
? About 1000 progeny of M13 are produced for generateion , thus, pure
single stranded copies of ds DNA insert are obtain in abudances using
m13 phage .
?The ds form of M13 is used to produce recombinate molecules . this
form is readily isolated from the infected E.Coli cells .
? The single stranded form of M13 is used to recover ss - insert from
phage praticles that are abundant in growth medium .

DISADVANTAGE
There is a limit to size of DNA fragment cloned with [ 1500 bp ]
maximum capacity and 3 kb have occasionaly been cloned .
REFERANCES
? www .bujus//.com
? https ://www.ncbi.nlm.nih.gov.
?www.sciencedirect.com
?Textbook in essential of microbiology - author S.RAJAN

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Ananthalakshmi [m13 bacteriophage].pptx

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Ananthalakshmi [m13 bacteriophage].pptx